1. Field of the Invention
The present invention relates generally to the study and uses of membrane glycoproteins. More specifically, the present invention provides a method of producing membrane-free membrane glycoproteins maintained in native conformation.
2. Description of the Related Art
Many membrane glycoproteins are assembled within cells in a highly constrained and energy rich conformation. The membrane proteins of membrane-containing viruses are examples of energy rich proteins. These proteins assemble in the endoplasmic reticulum (ER) through intermediates which are stabilized by disulfide bonds. Because of this high energy configuration it is difficult if not impossible to maintain these proteins in native conformation when extracting them from their associated membrane. Extracting these proteins from the membrane results in their collapse into a normative, relaxed configuration that makes structural analysis on these proteins difficult. In the case of virus membrane proteins, the normative conformation makes these proteins ineffective for use as subunit viral vaccines.
In the case of influenza virus, this conformation problem was overcome by the discovery of an accessible protease site in the HA1-HA2 membrane glycoprotein (Wiley and Skehel, 1977). This site allowed the release of the protein ectodomain upon treatment of intact virus with the protease. The released ectodomain retained its native conformation, thereby allowing the determination of its structure at atomic resolution by X-ray crystallography (Wiley and Skehel, 1977).
Most membrane proteins, however, do not contain an accessible protease site such as that found in influenza virus. This fact and the failure of other methods of protein purification have made it impossible to obtain these proteins in native conformation. Thus, the prior art is deficient in a method of producing membrane-free membrane glycoproteins maintained in native conformation. The present invention provides a solution to this long-standing need and desire in the art.